The invention is based on a device for determining a certain filling level in a container with an oscillation probe which has two oscillation elements which have the same resonance frequency and vibrate in two opposite directions of rotation. The elements are arranged spaced coaxially to one another, with the outer vibration element at least partially enclosing the inner oscillation element whereby the vibrations of the oscillation probe are damped when touching the filling material with the outer oscillation element. The drive of the oscillation probe and the detection of the oscillation amplitude occur by means of an electromechanical transformer in the form of piezo-electrical elements, as they, for example, are known from EP 0 089 336. Through this, a precise monitoring of the level of the filling material in the container is made possible, independent of the clamping conditions of the oscillation probe and for nearly every kind of filling material of great and little density.
The coaxially formed rotary oscillation systems had the disadvantage that the elastic or resilient mounting of both oscillation elements was provided separately by each of the two independent spring elements. Thus, the mutual driving of both oscillation elements was not possible.